Genetic variation of and environmental effects on inducibility of resistance in tomatoes (Solanum lycopersicum L.) to Phytophthora infestans (Mont) de Bary

Many plant strengtheners are promoted for their supposed effects on nutrient uptake and/or resistance induction (IR). In addition, many organic fertilizers are supposed to enhance plant health and several studies have shown that tomatoes grown organically are more resistant to late blight, caused by Phytophthora infestans to tomatoes grown conventionally. Much is known about the mechanisms underlying IR. In contrast, there is no systematic knowledge about genetic variation for IR. Therefore, the following questions were addressed in the presented dissertation: (i) Is there genetic variation among tomato genotypes for inducibility of resistance to P. infestans? (ii) How do different PS compare with the chemical inducer BABA in their ability to IR? (iii) Does IR interact with the inducer used and different organic fertilizers? A varietal screening showed that contrary to the commonly held belief IR in tomatoes is genotype and isolate specific. These results indicate that it should be possible to select for inducibility of resistance in tomato breeding. However, isolate specificity also suggests that there could be pathogen adaptation. The three tested PS as well as two of the three tested organic fertilisers all induced resistance in the tomatoes. Depending on PS or BABA variety and isolate effects varied. In contrast, there were no variety and isolate specific effects of the fertilisers and no interactions with the PS and fertilisers. This suggests that the different PS should work independent of the soil substrate used. In contrast the results were markedly different when isolate mixtures were used for challenge inoculations. Plants were generally less susceptible to isolate mixtures than to single isolates. In addition, the effectiveness of the PS was greater and more similar to BABA when isolate mixtures were used. The fact that the different PS and BABA differed in their ability to induce resistance in different host genotype -pathogen isolate combinations puts the usefulness of IR as a breeding goal in question. This would result in varieties depending on specific inducers. The results with the isolate mixtures are highly relevant. On the one hand they increase the effectiveness of the resistance inducers. On the other hand, measures that increase the pathogen diversity such as the use of diversified host populations will also increase the overall resistance of the hosts. For organic tomato production the results indicate that it is possible to enhance the tomato growing system with respect to plant health management by using optimal fertilisers, plant strengtheners and any measures that increase system diversity.

Interrelatedness of grazing livestock with vegetation parameters and farmers’ livelihoods in the Mahafaly region, southwestern Madagascar

The study aims to get deeper insight into the highly extensive system of animal husbandry in the Mahafaly region of southwestern Madagascar. It tries to understand the major drivers for pastoral dynamics, land and resource use along a gradient in altitude and vegetation to consider the area’s high spatial and temporal heterogeneity. The study also analyzes the reproductive performance of local livestock as well as the owners’ culling strategies to determine herd dynamics, opportunities for economic growth, and future potential for rural development. Across seasons, plateau herds from both livestock species covered longer distances (cattle 13.6±3.02 km, goats 12.3±3.48 km) and were found further away from the settlements (cattle 3.1±0.96 km, goats 2.8±0.98 km) than those from the coastal plain (walking_dist: cattle 9.5±3.25 km, goats 9.2±2.57 km; max_dist: cattle 2.6±1.28 km, goats 1.8±0.61 km). Transhumant cattle were detected more vulnerable through limited access to pasture land and water resources compared to local herds. Seasonal water shortage has been confirmed as a key constraint on the plateau while livestock keeping along the coast is more limited by dry season forage availability. However, recent security issues and land use conflicts with local crop farmers are gaining importance and force livestock owners to adapt their traditional grazing management, resulting in spatio-temporal variation of livestock numbers and in the impending risk of local overgrazing and degradation of rangelands. Among the 133 plant species consumed by livestock, 13 were determined of major importance for the animals’ nutrition. The nutritive value and digestibility of the natural forage, as well as its abundance in the coastal zone, substantially decreased over the course of the dry season and emphasized the importance of supplementary forage plants, in particular Euphorbia stenoclada. At the same time, an unsustainable utilization and overexploitation of its wild stocks may raise the pressure on the vegetation and pasture resources within the nearby Tsimanampetsotsa National Park. Age at first parturition was 40.5±0.59 months for cattle and 21.3±0.63 months for goats. Both species showed long parturition intervals (cattle 24.2±0.48 months, goats 12.4±0.30 months), mostly due to the maintenance of poorly performing breeding females within the herds. Reported offspring mortality, however, was low with 2.5% of cattle and 18.8% of goats dying before reaching maturity. The analysis of economic information revealed higher than expected market dynamics, especially for zebus, resulting in annual contribution margins of 33 € per cattle unit and 11 € per goat unit. The application of the PRY Herd Life model to simulate herd development for present management and two alternate scenarios confirmed the economic profitability of the current livestock system and showed potential for further productive and economic development. However, this might be clearly limited by the region’s restricted carrying capacity. Summarizing, this study illustrates the highly extensive and resources-driven character of the livestock system in the Mahafaly region, with herd mobility being a central element to cope with seasonal shortages in forage and water. But additional key drivers and external factors are gaining importance and increasingly affect migration decisions and grazing management. This leads to an increased risk of local overgrazing and overexploitation of natural pasture resources and intensifies the tension between pastoral and conservation interests. At the same time, it hampers the region’s agronomic development, which has not yet been fully exploited. The situation therefore demonstrates the need for practical improvement suggestions and implication measures, such as the systematic forestation of supplemental forage plant species in the coastal zone or a stronger integration of animal husbandry and crop production, to sustain the traditional livestock system without compromising peoples’ livelihoods while at the same time minimizing the pastoral impact on the area’s unique nature and environment.

Factors influencing the use of selected inputs in yam production in Nigeria and Ghana

In West Africa, yam can be an important crop to reduce poverty and hunger if Research and Development measures identify and properly engage its key production factors for enhanced outputs and better income. Data from 1400 households in Ghana and Nigeria were collected in a multistage random sampling survey (and complementary data from 76 farm family fields) with a structured questionnaire and qualitative interview questions. The results showed that yam is produced mainly with crude inputs/technologies to reduce high dependence on labour, seed production and control of pests and diseases. Yam is produced widely with purchased inputs including seed yam and hired labour; chemical fertiliser, herbicide and pesticides are less often used. Analyses of determinants of use of purchased inputs reveal three serious impediments to expansion in yam production: the increasing scarcity and high cost of hired labour, shortage of suitable land and poor farm roads. As employment opportunities for unskilled labour in urban centres are presently expanding, increased yam production will be hard to achieve without labour-saving inputs for at least some of the production tasks, especially seedbed preparation and weeding, and without improvement in infrastructure.

Herd management and livestock productivity in the Altai region of Western Mongolia

This thesis analyses the influence of qualitative and quantitative herbage production on seasonal rangelands, and of herd and pasture use strategies on feed intake, body mass development and reproductive performance of sheep and goats in the Altai mountain region of Bulgan county (soum) in Khovd province (aimag). This westernmost county of Mongolia is characterized by a very poor road network and thus very difficult access to regional and national markets. The thesis explores in this localized context the current rural development, the economic settings and political measures that affect the traditional extensive livestock husbandry system and its importance for rural livelihoods. Livestock management practices still follow the traditional transhumant mode, fully relying on natural pasture. This renders animal feeding very vulnerable to the highly variable climatic conditions which is one of many reasons for gradually declining quantity and quality of pasture vegetation. Small ruminants, and especially goats, are the main important species securing economic viability of their owners’ livelihood, and they are well adapted to the harsh continental climate and the present low input management practices. It is likely that small ruminants will keep their vital role for the rural community in the future, since the weak local infrastructure and slow market developments currently do not allow many income diversification options. Since the profitability of a single animal is low, animal numbers tend to increase, whereas herd management does not change. Possibilities to improve the current livestock management and thus herders’ livelihoods in an environmentally, economically and socially sustainable manner are simulated through bio-economic modelling and the implications are discussed at the regional and national scale. To increase the welfare of the local population, a substantial infrastructural and market development is needed, which needs to be accompanied by suitable pasture management schemes and policies